1. Field of the Invention
The present invention relates to lachrymal plugs and methods for positioning these devices.
The present invention is generally directed to controlling the flow of tears running from the surface of the eye towards the nasal cavity.
2. Discussion of Background Information
The normal functioning of the human eye requires that its outer surface be constantly covered with a lubricating film constituted by tears, that ensure both rinsing and protection due to the natural anti-infectious antibiotics that they contain. They are produced by a series of glands located in the eyelids and about the periphery of the eye.
The deficiency in maintaining the stability of this film on the eyeball can cause various nuisances, such as stinging, irritations, burning sensations and sight deterioration in the case of dryness on the eye surface.
Tears are produced continuously, the excess of fluid being drained from the eyeball surface 1 through two point openings constituting the upper 2 and lower 3 lachrymal points located near the inner corner of the eye and communicating with ducts known as canaliculi 4, 5, that lead to a lachrymal sac 6 that opens out into the nasal cavity 7. The lachrymal points 2, 3 are capable of opening or closing in the manner of a sphincter-type muscle, so as to ensure controlling the flow of the fluid (FIG. 1).
The lack of lachrymal fluid on the eyeball is generally due to a deficiency of the productive glands, which can be caused by age or by other factors.
It is possible to improve the situation by acting on the lachrymal ducts by completely or partially blocking them.
In particular, permanent blockage, possibly by surgery (cauterization, laser) of the lachrymal ducts, can be a method for treating tear-related deficiencies. When the flow of tears in the nasolachrymal sac is thus prevented, the volume of remaining tears generates greater moisture.
This method has the drawback of being irreversible, barring a new surgical intervention. To overcome this, removable devices capable of being positioned in a lachrymal duct and removed without surgical intervention have been proposed. For instance, U.S. Pat. No. 5,334,137, filed by “EAGLE VISION,” describes a device for controlling the lachrymal fluid that blocks the flow of this fluid originating from the surface of the eye, and comprising an inverted truncated cone-shaped end portion and a head provided with a widened dome. The end portion is arranged to facilitate the positioning of the device through a point opening, and the widened dome prevents the complete penetration of the device into the vertical portion of the canaliculus through the point opening.
Nevertheless, this type of device has risks of accidental migration or expulsion. Furthermore, it requires a special apparatus for positioning and extraction, and it does not allow increasing the flow of the lachrymal fluid.
International Publication No. WO 98/33461, filed by Mr. Alain Foueré, co-Applicant of the present application, describes a screwable meatus plug adapted to be implanted in the lachrymal points, and constituted of a substantially cylindrical body whose lateral surface comprises a helical threading, similar to that of a screw allowing to position it or remove it by screwing or unscrewing, the meatus plug comprising, or not, an axial through duct allowing the passage of a predetermined flow of lachrymal fluid.
However, this implant allows intervening only on the lachrymal points 2, 3, and not on the other parts of the tear flow system, such as the canaliculi 4, 5 (see FIG. 1).
Given their design, the dimensions of known systems must be adapted to the morphology of each patient, which requires a more or less wide range of prostheses of each type, resulting in an increase of the manufacturing and storing costs.